20x20x4 (3 5/8) Furnace Air Filters MERV 12 Pleated Plus Carbon 6 Pack rock-bottom too much will cause root

too much will cause root rot and plants will suffer

increasing the rate of chemical reactions which facilitate plant growth

Electrode replacement with the stainless steel round connector means there are no pins to bend or break during replacement

Use 2 – 3 teaspoons (10 – 15 ml) per gallon

20x20x4 (3 5/8) Furnace Air Filters MERV 12 Pleated Plus Carbon 6 Pack rock-bottom too much will cause rootImportant Note: Almost ALL furnace filters have a different "actual size" than the nominal size printed on the air conditioner filter. It's best if you measure your air filter for the EXACT size and compare it to our "Actual Size" and then you can be sure your A C air filter fits! With the 4" and 5" air filters there is a wider variance between the nominal and actual size depending on the manufacturer. If you are replacing a 4 3 8 depth 20x20x4 filter